The first four works written by St. Augustine of Hippo after his conversion to Christianity are dialogues that have influenced prominent thinkers from Boethius to Bernard Lonergan. Usually called the Cassiciacum dialogues, these four works are of a high literary and intellectual quality, combining Ciceronian and neo-Platonic philosophy, Roman comedy and Vergilian poetry, and early Christian theology. They are also, arguably, Augustine's most charming works, exhibiting his whimsical levity and ironic wryness. This book is the fourth work in this tetralogy. Augustine coined the term “soliloquy” to describe this new form of dialogue. The book, a conversation between Augustine and his reason, fuses the dialogue genre and Roman theater, opening with a search for intellectual and moral self-knowledge before converging on the nature of truth and the question of the soul's immortality. The volume also includes On the Immortality of the Soul, which consists of notes for the unfinished portion of the work.